广西大瑶山古罗碱性辉长岩体 LA-ICP-MS 锆石 U-Pb 年龄、岩石学、地球化学及其构造意义

摘要

古罗碱性辉长岩体包括古罗、黄羌冲两个侵入体，主要由辉长岩、石英辉长岩（或石英闪长岩）组成。岩石以富碱、富集大离子亲石元素（LILE）、轻稀土元素（LREE）和高场强元素（HFSE），无 Nb、Ta 异常，是典型的板内钾玄岩。对古罗辉长岩体进行了高精度的 LA-ICP-MS 锆石 U-Pb 定年，获得石英辉长岩的206Pb/238U 加权平均年龄为165.63±0.95 Ma。研究认为古罗碱性辉长岩体形成于中侏罗世，属典型的板内钾玄岩，形成于大陆地壳伸展拉张减薄的构造背景，为燕山期早期华南后造山阶段的地质记录。%Guluo alkaline gabbroic magmatic rocks including Guluo and Huangqiangchong intrusive rocks are comprising of gabbro, quartz-gabbro (or quartz-diorite). These rocks are enriched in alkalies, LILE, LREE and HFSE, characteristed by no Nb and Ta anomalies, which indicates belongs to typical intrapate-shoshonite series. Zircon LA-ICP-MS U-Pb dating of Guluo alkaline gabbroic rocks yields the 206Pb/238U age of 165.63±0.95 Ma. The geochronology data suggests that Guluo alkaline gabbroic rocks as typical intrapate-shoshonite series was formed in the Middle Jurassic Period, and indicated that the magma was generated in the tectonic settings of con-tinental crust extension and thinning, which records post-orogenesis event of South China in the Early Yanshan-nian period.